1. Field of the Invention
This invention relates to photography and to novel chemical compounds useful therein. More particularly, it relates to novel chemical compounds useful in the development of photosensitive silver halide materials and to photographic products, processes and compositions employing the same.
2. Description of the Prior Art
In the photographic art, developing agents are employed to convert the exposed silver halide to metallic silver. The most common of these developers has been, until recent years, hydroquinone and hydroquinone derivatives, para-aminophenol and para-phenylenediamine. However, there has been an increasing interest in recent years in heterocyclic developing agents, i.e., developing agents containing a heterocyclic ring as part of their structure. Some of these developing agents have the conventional hydroxyl or amino developing groups substituted on adjacent carbon atoms of a heterocyclic ring to provide structures similar to those of the developing agents in the aliphatic and aromatic series. Still other heterocyclic developing agents as exemplified by 1-phenyl-3-pyrazolidinimine and 1-phenyl-3-pyrazolidone (commercially available under the trademark "Phenidone") have one of the functional developing groups included as part of the heterocyclic ring. 1-Phenyl-3-pyrazolidinimine forms the subject matter of British Pat. No. 757,840 and 1-phenyl-3-pyrazolidone and its 4,4-dialkyl derivatives form the subject matter of U.S. Pat. Nos. 2,289,367 and 2,772,282 respectively. The best known of these developing substances, viz 1-phenyl-3-pyrazolidone itself possesses only poor developing properties as far as its development in aqueous medium is concerned [J. D. Kendall, British Journal of Photography (1951) 539]. The commercial significance of the above-identified developing agents in general, therefore, rests primarily in their ability to form superadditive mixtures with other developing agents, for example, hydroquinones.
The present invention is concerned with novel silver halide developing agents some of which are in addition, novel heterocyclic compounds, and all of which are useful in conventional and in diffusion transfer photography, both black-and-white and color.